Branched chain keto dehydrogenase of Pseudomonas putida is an unusual enzyme whose activity is stimulated by L-valine. The enzyme has been purified to a specific activity of 10 units/mg protein. The purified enzyme contains 4 subunis with molecular weights of 49k, 46k, 39k, and 37k. The 49k protein has been isolated and identified as lipoamide dehydrogenase. The objective of the current year will be to isolate and identify the remainding subunits. The transacylase subunit will be identified by its specific labeling with N-ethyl(2,3-14C) maleimide in the presence of 2-ketoisovalerate. The dehydrogenase (E1) subunit will be identified by its reaction with ferricyanide and the release of radioactive carbon dioxide from 2-keto(1-14C) isovalerate.